The molecular mechanism by which brief periods of neuronal activity leads to long-lasting changes in the nervous system is thought to involve activation of novel patterns of gene expression, which results in alteration of the physiology of the cell. To understand the mechanisms by which chronic pain and nerve injury alter the nervous system, as well as to identify putative biological regulators involved in these conditions, the molecular mechanisms behind pain and nerve injury need to be better understood. The best characterized genes which are regulated by the pain and nerve injury pathways in the nervous system are the neuropeptide genes. These genes contain unique combinations of cis-acting DNA elements through which signaling has been demonstrated to occur in vitro. Furthermore, individual neuropeptides demonstrate differential responsiveness to the same stimulus making them ideal endogenous "reporter genes" for studying signal transduction of specific stimuli in the nervous system. Using standard gel shift methods, we have demonstrated that spinal cord proteins that bind to the enkephalin enhancer sequences are different from those that bind either chromaffin cells or PC12 cells. Furthermore, this binding activity is specific for the enkephalin enhancer since it can differentiate between enhancers with a similar core sequence but different flanking sequences. Therefore, transcription factors which bind to the enkephalin gene, and likely other neuropeptide genes, are both tissue specific and highly selective for target DNA elements within a tissue. Using neuropeptide genes at the level of the spinal cord and dorsal root ganglia that are responsive to nerve injury and pain, we will focus on identifying transcription factors which are specific for these signaling pathways in vivo.